In imaging with an X-ray unit, for example with an X-ray computed tomography unit, which has an X-ray recording system with an X-ray source and an X-ray detector, the aim is to design the detection surface of the X-ray detector which is available for image acquisition to be as large as possible in order, for example, to be able to scan whole organs, such as the heart of a patient, in one course of the X-ray system. Such an X-ray detector, also denoted as a flat detector, is constructed as a rule from a multiplicity of detector modules that are aligned with respect to one another in two dimensions. Each detector module has an array of scintillator elements and an array of photodiodes that are aligned with respect to one another. A scintillator element and a photodiode in this case form a detector element of the detector module. A detector element represents a pixel of the detector. The scintillator elements convert X-radiation impinging on them into visible light that is converted into electric signals by the downstream photodiodes of the array of photodiodes.
In specific instances of medical diagnosis, it is desirable to be able to use the X-ray machine to produce images of an examination object that have a higher spatial resolution than the spatial resolution of the X-ray detector used, which spatial resolution is prescribed by the raster of the detector elements or the raster of the pixels. For this purpose, it is known from DE 101 45 997 A1 to use a high resolution diaphragm that has closely adjacent diaphragm slots and is formed from a material, usually from a heavy metal, that absorbs X-rays. The high resolution diaphragm shades a portion of each pixel of the array of scintillator elements such that in each case X-radiation is applied only to a portion of a scintillator element, the result being to achieve a higher spatial resolution. In order to achieve a higher spatial resolution, however, only a portion of the X-radiation which has passed through the patient is used for imaging.
In order, in addition to X-ray pictures with a spatial resolution corresponding to the raster of the pixels, also to be able to obtain X-ray pictures of higher spatial resolution, the high resolution diaphragm can, as a rule, be moved by motor between an operating position and an axially offset non-operational position. Consequently, on the X-ray recording system there is additionally a moving component, specifically the high resolution diaphragm, which has to be adjusted for operation, and for which additional resolution space must be made available on the X-ray recording system in order, in the case of nonuse, to be able to take up the high resolution diaphragm such that it is not prevented from acquiring other images using the X-ray recording system. Moreover, moving the high resolution diaphragm into an operating position and into a non-operational position requires a complicated and very expensive mechanism.